“A long time ago in a galaxy far, far away” doesn’t even begin to describe a small, bright galaxy hovering at the edge of the observable universe. The little cluster of stars, called GN-z11, is the most distant object astronomers have spotted: It existed when the universe was just 400 million years old.
“This is a very early galaxy,” says UC-Santa Cruz’s Garth Illingworth, who described the galaxy in The Astrophysical Journal. “We’re looking back 13.4 billion years, through 97 percent of all time, to the galaxy when it was forming.”
Yep, it took 13.4 billion years for light from the galaxy to zoom through the universe and collide with the Hubble Space Telescope. But that doesn’t mean the galaxy is 13.4 billion light-years away. The universe has been expanding in the meantime, meaning GN-z11 is actually much, much farther from Earth than that.
“Right now, we expect this galaxy to be about 32 billion light-years away from us in distance,” says study coauthor Pascal Oesch of Yale University.
In other words, the galaxy existed a ridiculously long time ago and is really, really, absurdly far away. To put it politely.
A Precocious Star Factory
When you peer into the distant universe, you’re also looking back in time. So the galaxy in its present form would look very different than what Hubble sees now.
But 13.4 billion years ago, this bright little knot of a billion stars was about 1 percent the size of the Milky Way. Despite its size, the precocious galaxy was pumping out stars much more quickly than the Milky Way. Those stars were very hot, very young, and very massive—the types of stars astronomers think existed in the early universe.
They just didn’t expect to see them so soon.
“We really did not expect to find a galaxy this bright, this early, in the history of universe,” Oesch says. “The big question is, how common are galaxies this bright so early in cosmic history? I don’t think there’s too many out there. I think we were lucky.”
Not For Long
History has taught us that astronomical distance records don’t hold up for long. The previous most-distant galaxy, called EGSY8p7, was reported in July 2015. It’s about 200 million or 300 million years younger than GN-z11, and has a redshift of 8.68. (Redshifts measure how much light has stretched as it travels through the cosmos; higher redshift values correspond to greater distances.) Before that? The winner was EGS-zs8-1, a galaxy that’s another 200 million years younger, and was reported in February 2015. It has a redshift of 7.78.
The new record-holder is at redshift 11, which is a number I hadn’t really expected to see at this point. For what it’s worth, light from the cosmic microwave background—a remnant of the Big Bang—has a redshift of 1,089.
Each newer, sharper eye in the sky reveals ever more distant and intriguing objects. So even though GN-z11 is the winner for now, it’s likely to hold onto its title for less time than an Olympic gold medalist. In 2018, the James Webb Space Telescope will launch, and if everything goes well, its ability to peer back in time will be even more impressive than Hubble’s.
“We’re basically at the limit of Hubble,” Illingworth says. “If you go out a little bit further, there is no light. Hubble can’t see anything.”